Manufacture of paraffin wax



United States Patent 2,737,470 MANUFACTURE or PARAFFIN WAX Stephen F. Perry, Westfield, Randolph M. Bailly, Little Silver, and Herman I. Zoeller, Union, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application March 14, 1952, Serial No. 276,518

3 Claims. (Cl. 196-20) The present invention is concerned with the production of a high quality parafiin wax. The invention is more specifically directed toward the removal of small traces of oil from the wax in order to stabilize the wax against subsequent deterioration. In accordance with the present invention, a small quantity of a highly refined oil is added to the wax prior to sweating the same under conditions to secure substantially complete removal of the deleterious oil constituents.

In the refining of hydrocarbon oils such as petroleum oils, it is known to segregate parafiin waxes from so-called paraffin distillates, waxy lubes and the like. The segregation of these waxes is secured by a number of processes. For example, it is known to chill the selected wax-containing fraction in order to secure crystallization of the wax and to remove the wax crystals from the oil by filtering, centrifuging and the like. It is also known to use various dewaxing solvents as liquid normally gaseous hydrocarbons, such as propane, butane, as well as other solvents, such as methyl-ethyl ketone and the like. It is also known to utilize in dewaxing operations solvent mixtures wherein one solvent comprises a wax precipitating solvent while the other comprises a solvent having a high solubility for oil. A solvent mixture of this character, for example, comprises 60% by volume of toluene and 40% by volume of methyl-ethyl ketone. In utilizing a mixture of this character, it has been the practice to add the mixture in toto or incrementally to the waxy distillate as it is being chilled. In dewaxing operations, ,it is also known to use various filter aids and other agents in order to render the dewaxing and filtering operationsmore eflicient.

' The wax segregated from the hydrocarbon oil, usually termed, slack wax, contains from about 10% to 40% ofoiL. The slack wax is refined usually by conventional sweating to produce crude scale wax in a manner to reduce the oil content to less than about 5% by weight. The slack wax may be distilled to obtain the desired boiling range prior to sweating, if desired. This crude scale wax generally has an oil content of about 2% to 3% by weight. In order to remove this oil from the scale wax to' produce a refined wax having an oil content below about .5%, usually below about 3%, various procedures have been proposed and employed, as for example, solvent deoiling operations and sweating procedures.

In the manufacture of refined paraffin wax from the wax-bearing petroleum distillates, conventional processing sequenceicalls for an initial dewaxing step to remove the bulk of the oil from the wax-bearing stream, deoiling the resultant wax to a suitable oilcontent, chemical treating the low 'oil content wax in order to stabilize the oil, and finally bauxite or clay filtering to improve color, odor-and taste. One of the quality tests that the finished paraflin wax product is required to meet is the National Formulary (N. F.) acid test. This test is designated as A. S. T. M. D612-45 and is a measure of purity and determines the relative amounts of carbonizable material in the wax. By spectroscopic studies it has been determined that the oil remaining in the wax contains the constituents responsible for the parafiin wax passing or not passing the National Formulary (N. F.) purity test. Therefore, any treatment given the oil, per se, will be reflected in the quality of the finished refined wax. Further spectroscopic studies have indicated that the 2 and 3 ring aromatic constituents in the oil contained in the wax are responsible for the failure of the wax to pass the N. F. acid test for purity. In fact, optical density or absorptivity at 330 millimicrons wavelength, in the ultraviolet region, which is a reflection of condensed aromatic content, has been found to correlate with N. F. acid test in a straight line relationship described by the following formula:

N. F. acid test=7650 times K330 when K330 is the optical density in units of liters/gm.-cm.

Acid treating the wax, as expected, does improve the N. F. acid test on refined wax due to the acid reacting with the 2 and 3 ring aromatics. The reaction products are removed by neutralization and water washing. Deoiling and melting point separation by sweating will also reduce the 2 and 3 ring aromaticsin the paraffin wax as the oil content is reduced. However, sweating alone will not reduce the aromatic content sufficiently low enough for the wax to pass the N. F. acid purity test without a further chemical treatment unless the sweating is carried out to an uneconomical extreme. The final percolation step through bauxite or clay also reduces the N. F. acid test indication but only approximately 50% under normal conditions. This is not sufiicient for obtaining a parafiin wax of the desired purity as measured by passing the N. F. test.

In accordance with the present invention, instead of acid treating the wax, which requires large quantities of chemicals, extraneous equipment and also presents sludge disposal problems, the scale wax prior to sweating is blended with a small quantity of a highly refined oil, which preferably is prepared by acid treating. By this procedure the concentration of 2 and 3 ring aromatics in the oil contained in the wax is materially reduced. Furthermore in the subsequent sweating operations the bulk of the added refined oil is removed in the initial sweater cuts without adversely affecting sweater yields.

The process of the present invention may be fully understood by reference to the drawing illustrating one embodiment of the same. Referring specifically to the drawing,

a waxy crude oil is introduced into distillation zone 1 by means of feed line 2. Temperature and pressure conditions in zone 1 are adapted to remove overhead by means of lines 3 and 4 the low boiling hydrocarbon fractions. A waxy distillate fraction is removed as a side stream by means of line 5, while a residual oil is removed by means of line 6.

The waxy distillate flows through a chilling zone 7 which may comprise a plurality of chilling stages wherein the temperature of the waxy distillate is progressively reduced. A typical operation is to introduce the feed Pnrafiin is listed in the National Formulary with specifications which include that it must pass the N. F. acid test. This test is applicable to paraffin wax to ascertain whether it conforms to the standard of quality required for pharmaceutical, food and drug uses.

The test procedure is as follows: 5 ml. of wax and 5 ml. of 94.7% 0.2) sulfuric acid are contacted at 157 F. for six minutes with intermittent mixing and settling intervals. The resultant color of the ac d layer is compared with a standard color system. An arbitrarily chosen color standard of 5 or less is considered satisfactory. A color darker than 5 is coin sidered not passing. If not passing the paraffin wax contains carbonizable material making it unfit for use in connection with cosmetics, foods and drugs.

3 oil into an initialchillingkstage at a temperature of about 135). F .;.t,o introduce the feed oil into the second chilling stage at a temperature of about 90 F.; to introduce the feed oil to the third chilling stage at a temperature of about- 60 F.; to introduce the'feed oil to the-fourth chilling stage -at--a temperature of about 25 and to chill the-same-in thefourth--chilling-stage?t a temperature irrthe range'from about to +10- -HF. The operation of the respective chilling stages may be varied appreciably and either direct or indirectzchilling means utilized. For-purposes of illustration; it is 'assumed 'that a; solvent mixture is used and that the wax-precipitant comprises methyl-ethylsketone and thatthe aromatic solvent havinga high solubilityfor oilcomprises toluene.

It, is also assumed that 3 to 4 volumes-of total-solvent mixture is utilized per volume of waxy-oilbeingvdewaxed. The solventmixture comprises 75% by volume of methyl-ethyl? ketone and-25% by volume of toluene.

Theentire mixture-comprising ,oilyconstituents, -crys-- tallized =wax constituents,- toluene and methyl-ethyl ketone, after} chilling is'held' at the filtering temperature and passed to filtering zone 8 wherein the-solid wax particles are segregated from the oily constituents by any suitable filtering or separation means. The filtering zone may comprise drum filters, plate and frame presses,centrifuges or suitable equivalent equipment for the separation of the precipitated waxy constituents from the oily constituents. The oil and a portion of the solvent is re moved from zone 8 by means of line 9 and the wax cake washed with a wash solvent-introduced into filtering-zone 8193 means of line 10. Slack wax and solvent are removed "from zone 8 by means of 1ine-11 and passed to a distillation zone 12-wherein a separation is made between the wax and the solvent. It is to be understood that other means of separating the solvent from the wax maybe utilized if desirable.

The wax substantially free of solvent is removed from separation zone 12 by means of line 13. The solvent mixture comprising methyl-ethyl ketone and toluene is removed overhead from zone 12 by means of line 14 and preferably recycled to the system. The oil-solvent mixture removed from filtering zone 8 by means of line 9 is introduced into a distillation zone wherein a separation is made between the oily constituents and the sol vent mixture.

While the drawing illustrates a solvent dewaxing operation with respect to the production of the slack wax, itis to be understood that the waxy constituents may also be separated in a conventional plateandframepressing operation. Theslack wax may be further refined'to crude scale wax in zone 15, -which comprises a conven tional sweating operation, 'orsolvent deoiling operation, or the like. The oil removed from zone 15 by means of line 36 may preferably be recycled -to zone 7.' The scale Wax is removed from zone 15 by means of line35 and maybe further refined-by treatment with sulfuric acid or fullers earth, bauxite or other absorbent materials, or by hydrogenation under mild treating conditiOliS.

However, in accordance with the present invention, a highly refined oil is addedto the scale wax bymeans of line 50. The mixture is passed to sweating zone 16 wherein the same is exposed to progressively higher temperatures. By this procedure-the quantityof 2 and 3 ring aromatics in the wax product is'materially reduced. The bulk of'these compounds isremoved from thesweated wax by means of line 51. Wax fractions of desirable quality are removed from zone 16 by means of line 29.

The invention is broadly concerned with the removal of multicyclic ring oily constituents from scale wax :in orderto improve the quality of the wax. This is secured by adding to the wax from '1 to 4 volumes of a highly refined oil, per-volume of .o'il remaining in the scalewax, and then" subjecting the-same "to a sweating operation.

Preferred oils are, white oils or highly refined'lub'rieating oils. These oils are produced preferably by the action of fuming sulfuric acid on selected petroleum distillate fractions. A typical white oil specification is as follows:

Final F..' .680 'to 750 Oils satisfactory for the purpose of this invention, i. e., extremely low in content of condensed ring aromatics, might also be made by methods other than acid tre'ating for example by exhaustive selective extraction or by hydrogenation of the naturally occurring aromatics. It is desired that the oil used be low enough in condensed aromatic so that the presence of 0.1% of this oil, in a conventionally refined paralfin wax, will not raise its N. F. acid test by more than 1 on the rating scale, and it is preferred that it be completely inert in this test; It is also preferred that the oil be low in viscosity, in order to obtain maximum sweating efficiency.

The process of the present invention may be more-fullyunderstood by the following examples illustrating the same.

Example 1 A scale wax was produced by segregating a waxy distillate in an atmospheric and vacuum distillation operation. The waxy distillate had a boiling range of 10 millimeters absolute pressure of about 350 Fl to 600.F.

and contained about 45% wax. The waxy distillate was dewaxed utilizing ethyl-methyl ketone to produce a slack wax having an oil content of about 10%." The slack wax was sweated to a scale wax of the followin gimspections:

Melting point, F. 124 Oil content- (ASTM), wt. percent 1.6

In oneoperation this scale wax was diulted with whi te oil prior to further sweating and in another operation was not diluted with a white oil. The white oil used had the following properties:

The sweated wax was filtered through bauxite at F. temperature. followsz Sweating of untreated crude scale to refined wax with and without white oil dilution SWEATED PRODUCTS (BAUXITE FILTERED'25-T/T) 1 Arating of 5 or lower is satisfactory. I ASTM-DBIHE.-

The resultsof these operations are as As will be noted in the above table, the added white oil was largely removed in the early part of the sweating, taking with it the bulk or the'undesirable constituents causing a high N. F. acid test. As a result, a much lower N. F. acid test was obtained at the same sweater yield when using the white oil, enabling the N. F. acid test specification to be passed.

' Example 2 Wax Oil Content, Wt. Percent Sweater Yields Four to One Dilution With White Oil No White Oil Added FF? argue/micro en en commune ox Or What is claimed is:

1. Process for the production of a high quality paraffin wax of improved stabi1ity,'which comprises segregating a scale wax having an oil content of less than about 3% by weight, thereafter adding to said scale wax from about 1 to about 4 volumes, based on the oil content of said scale wax, of a lubricating oil which has been treated with concentrated sulfuric acid, and

thereafter sweating the wax-oil mixture to a low oil content.

2. The process according to claim 1 wherein said oil treated with sulfuric acid is white oil.

3. The process according to claim 1 wherein said oil treated With sulfuric acid is characterized by being substantially inert in the National Formulary acid test.

References Cited in the file of this patent UNITED STATES PATENTS 1,037,518 Henderson et al. Dec. 5, 1933 2,117,984 Richardson et al May 17, 1938 2,164,779 Manley July 4, 1939 

1. PROCESS FOR THE PRODUCTION OF A HIGH QUALITY PARAFFIN WAX OF IMPROVED STABILITY, WHICH COMPRISES SEGREGATING A SCALE WAX HAVING AN OIL CONTENT OF LESS THAN ABOUT 3% BY WEIGHT, THEREAFTER ADDING TO SAID SCALE WAX FROM ABOUT 1 TO ABOUT 4 VOLUMES, BASED ON THE OIL CONTENT OF SAID SCALE WAX, OF A LUBRICATING OIL WHICH HAS BEEN TREATED WITH CONCENTRATED SULFURIC ACID, AND THEREAFTER SWEATING THE WAX-OIL MIXTURE TO A LOW OIL CONTENT. 